Hi, more an electrical question than a programming issue -- I have a Teensy 3.6 I'm using to produce audio directly with the DAC. I'm powering the Teensy with a 3.8V switching regulator, and using it in 3.3Vref mode. What I see is enough power supply noise appearing on the DAC output that it's requiring much more filtering than I anticipated.
This seems like reasonable behavior when using the V+ as a voltage reference, but I'm surprised so much noise in the audible range is making it through the onboard 3.3V linear regulator. Is this normal? I'd love to switch to the 1.65V internal reference, but that doesn't have the voltage output I need and adding extra amplifiers on it seems like overkill.
Can I improve this by providing a higher Vin? Is there a filter capacitor for the AVDD/AVSS on the Teensy I can augment? Perhaps an inductor somewhere to smooth things out?
Right now the only thing that helps much is to attach inductors on my audio output wires, which will be added to my next design as surface mount components. But this has it's own issues as it does reduce the overall frequency range needlessly since the noise is all pre-DAC stage. If I can get a clean reference voltage, hopefully this would be better? Or is the recommended solution to just use the 1.65V internal regulator and put on an output stage with a gain of 2?
This seems like reasonable behavior when using the V+ as a voltage reference, but I'm surprised so much noise in the audible range is making it through the onboard 3.3V linear regulator. Is this normal? I'd love to switch to the 1.65V internal reference, but that doesn't have the voltage output I need and adding extra amplifiers on it seems like overkill.
Can I improve this by providing a higher Vin? Is there a filter capacitor for the AVDD/AVSS on the Teensy I can augment? Perhaps an inductor somewhere to smooth things out?
Right now the only thing that helps much is to attach inductors on my audio output wires, which will be added to my next design as surface mount components. But this has it's own issues as it does reduce the overall frequency range needlessly since the noise is all pre-DAC stage. If I can get a clean reference voltage, hopefully this would be better? Or is the recommended solution to just use the 1.65V internal regulator and put on an output stage with a gain of 2?